Interpretive Summary: Citrus greening is a disease that threatens the survival and economic viability of the Florida Citrus Industry due to the disease’s ability to kill an infected tree. An insect called an Asian Citrus Psyllid is a carrier of the bacterium that causes citrus greening; therefore, citrus growers are using several insecticides and sprayers to find the most effective method to control the insect. A number of studies involving numerous citrus sprayers and active ingredients were conducted to determine the droplet size generated by the different sprayers, and specify how to adjust the sprayers to meet a droplet size requirement that is on many insecticide labels. In the sprayer tests, it was found that reductions in engine speed or increases in flowrate were required to increase droplet sizes to meet the product label required droplet size. As the equipment tested here represents the most typical application equipment used in Florida for psyllid control, these results will provide applicators, growers, and extension agents with general guidelines to insure that spray systems are operated in a manner that complies with label restrictions.

Technical Abstract:
The Asian citrus psyllid (Diaphorina citri Kumayama, Sternorrhyncha: Psyllidae) is a detrimental pest to citrus crops when it serves as a vector of the pathogen that causes greening (huanglongbing, or HLB). Transmission of this disease causes mottling, chlorosis, dieback and reductions in both fruit size and quality. Citrus producers have found that many pesticides, when applied properly, are very effective at suppressing or eliminating citrus psyllids in groves. Due to threat of greening, several pesticides have been granted special local needs registration for use in the State of Florida if the product is sprayed with a volume median diameter of 90 microns or greater. A number of studies involving numerous citrus sprayers and active ingredients were conducted to determine the droplet size generated by the different sprayers operating under user established settings, and specify the adjustments required to those settings in order for the sprayers to meet the 90 micron requirement. In the sprayer tests, it was found that reductions in engine speed or increases in flowrate were required to increase droplet sizes to meet the product label required droplet size. As the equipment tested here represents the most typical application equipment used in Florida for psyllid control, these results will provide applicators, growers, and extension agents with general guidelines to insure that spray systems are operated in a manner that complies with label restrictions.